HOW IT WORKS: Voters rank the candidates in order of preference (ie, 1,2,3,4 instead of 'x'). If no candidate gets more than half the votes cast, the one who has fewest first preference votes has his or her votes reallocated, according to voters' second preferences. This continues until one candidate has more than half.

PROS: Retains the constituency link. Majority support at the local level, not just nationally.

CONS: Constituencies may be decided by the second preferences of the voters who supported the least popular candidate. Why should it be their second prefences which swing the constituency?